Second-generation IL-2 receptor-targeted diphtheria fusion toxin exhibits antitumor activity and synergy with anti–PD-1 in melanoma

Laurene S. Cheung, Juan Fu, Pankaj Kumar, Amit Kumar, Michael E. Urbanowski, Elizabeth A. Ihms, Sadiya Parveen, C. Korin Bullen, Garrett J. Patrick, Robert Harrison, John R. Murphy, Drew M. Pardoll, William R. Bishai

Research output: Contribution to journalArticlepeer-review


Denileukin diftitox (DAB-IL-2, Ontak) is a diphtheria-toxin–based fusion protein that depletes CD25-positive cells including regulatory T cells and has been approved for the treatment of persistent or recurrent cutaneous T cell lymphoma. However, the clinical use of denileukin diftitox was limited by vascular leak toxicity and production issues related to drug aggregation and purity. We found that a single amino acid substitution (V6A) in a motif associated with vascular leak induction yields a fully active, second-generation biologic, s-DAB-IL-2(V6A), which elicits 50-fold less human umbilical vein endothelial cell monolayer permeation and is 3.7-fold less lethal to mice by LD 50 analysis than s-DAB-IL-2. Additionally, to overcome aggregation problems, we developed a production method for the fusion toxin using Corynebacterium diphtheriae that secretes fully folded, biologically active, monomeric s-DAB-IL-2 into the culture medium. Using the poorly immunogenic mouse B16F10 melanoma model, we initiated treatment 7 days after tumor challenge and observed that, while both s-DAB-IL-2(V6A) and s-DAB-IL-2 are inhibitors of tumor growth, the capacity to treat with higher doses of s-DAB-IL-2(V6A) could provide a superior activity window. In a sequential dual-therapy study in tumors that have progressed for 10 days, both s-DAB-IL-2(V6A) and s-DAB-IL-2 given before checkpoint inhibition with anti–programmed cell death-1 (anti–PD-1) antibodies inhibited tumor growth, while either drug given as monotherapy had less effect. s-DAB-IL-2(V6A), a fully monomeric protein with reduced vascular leak, is a second-generation diphtheria-toxin–based fusion protein with promise as a cancer immunotherapeutic both alone and in conjunction with PD-1 blockade.

Original languageEnglish (US)
Pages (from-to)3100-3105
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number8
StatePublished - Feb 19 2019


  • Cancer immunotherapy
  • Fusion toxin
  • Tregs

ASJC Scopus subject areas

  • General


Dive into the research topics of 'Second-generation IL-2 receptor-targeted diphtheria fusion toxin exhibits antitumor activity and synergy with anti–PD-1 in melanoma'. Together they form a unique fingerprint.

Cite this